The incongruence between the United Nations objective to hold global warming well below 2 °C and the rate of global emission reductions has intensified interest in negative emissions. Previous research has explored several pros and cons of individual negative emissions technologies. Systematised approaches to comparing and prioritising among them are, however, largely lacking. In response to this gap in the literature, this article reviews the scientific literature on indicators for designing negative emissions climate stabilisation value indexes. An index typically provides summary measures of several components, often denoted indicators. Utilizing a narrative review methodology, the article derives five categories of indicators underpinned by overlapping and often mutually reinforcing environmental and socio-economic values. A list of 21 indicators are proposed to capture both positive and negative values associated with effectiveness, efficiency, scale, risk, and synergies. While discussing indicators capable of providing guidance on negative emissions is timely, given the emerging shift away from pure emission reduction targets towards net-zero targets, numerous complexities are involved in determining their relative values. The results herein serve to inform policy making on the prioritisation and incentivisation of negative emissions technologies capable of delivering on the new objectives, and the results highlight the many risks and uncertainties involved in such exercises. The article concludes that systematic research on the comparison of NETs is incomplete. An iterative, interdisciplinary research programme exploring such questions has the potential to be extremely rewarding.
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